Process for rendering nitrous gases innocuous



Patented Mar. 23, 1954 UNITED STATES PATENT OFFICE PROCESS FOR RENDERING NITROUS GASES INNOCUOUS Pierre Barman, Barcelona, Spain, assignor to Ciba Limited, Basel, Switzerland, a Swiss firm No Drawing. Application April 14, 1950, Serial No. 156,037

Claims priority, application Switzerland June 1'7, 1949 4 Claims. (Cl. 23220) It has already been proposed to absorb such gases in a very wide variety of absorption media in order to prevent their discharge into the at mosphere. If it is to be effective such absorption plant must be of very large dimensions and thereforecccupies considerable space and necessitates considerable installation costs. In many cases these disadvantages are not counterbalanced by the advantage of recovering nitric acid or nitrous acid or salts of these acids, and this is especially the case where the reaction yielding the nitrogen oxide gases is operated only occasionally. Consequently, there is a need for a simple method of rendering such gases innocuous.

The present invention provides a method for rendering nitrogen oxide gases innocuous, of which the requirements for apparatus and space are small, wherein the gases are mixed with a flame. i

In carrying out the present invention there may be used, for example, flames produced by burning gas, for instance, methane or ordinary illuminating gas, or by burning solid or liquid fuel, such as coal, benzine, oil and especially mazout which is frequently used for heating purposes. In order to bring out a thorough mixture of the nitrogen oxide gases with the flame, the said gases may, for example, be blown or sucked laterally into the flame at such a high speed that a turbulent flow results, or the gases may be supplied, with suitable modification in the construction of the burner used, directly to the space where the fuel is found or where it is discharged into the flame, because by producing a mixture of the nitrogen oxide gases and fuel a mixture of the said gases and the flame necessarily results.

Advantageously in producing the mixture the nitrogen oxide gases are led into the reducing portion of the flame. This requirement is nearly always fulfilled in practice when care is taken to produce a proper mixture of the nitrogen oxide gases with the flame, because almost any flame which can be produced technically has a reducing portion. However, it is not essential to operate the flame as a whole with a deficiency of atmospherie oxygen, because the attainment of a high flame temperature is advantageous for carrying out the present method. It is known that the dissociation of nitrogen peroxide into nitric oxide and oxygen occurs between and 620 C., and that at temperatures above 700 C. nitric oxide partially decomposes into nitrogen and oxygen. However, it could not be foreseen that it would be possible to render nitrogen oxide gases innocuous by the simple method of this inven-- tion.

The reaction is advantageously carried out in a horizontal or vertical furnace chamber lined with heat resistant material, for example, chamotte bricks, while about 2000 to 3000 kilogram calories of heat should be developed by the flame per kilogram of nitrogen peroxide supplied. In certain cases, for example, when the gases are highly dilute or when they contain much water vapor, somewhat larger quantities of heat may be reguired in order to decompose the nitrogen peroxide completely.

The following examples illustrate the invention:

Example 1 A gas flame was burnt in a vertical furnace chamber lined with chamotte bricks and nitrogen peroxide was led into the center of the gas outlet openings. In order to decompose the nitrogen peroxide completely the following quantities of gas were required:

F t 1?:gation Parts B Pzlirtsiiyf k .xperimeu 0 xperlv0 ume o g. cal. per

No. ment,minwail of illuminatkg. No,

utcs 2 ing gas The relationship of parts by weight to parts by volume is the same as that of the kilogram to the liter.

Example 2 A mazout flame was burnt in a burner operated with air under pressure in a horizontal furnace chamber 1.3 meters in length and 7 centimeters in diameter. A gas mixture containing in addition to nitrogen peroxide and nitric oxide about 40 per cent. of air and water vapor were supplied to the flame at an angle to the axis of the furnace chamber a short distance from the burner opening. Owing to the suction of the burner operated with compressed air a turbulent motion was produced. In this chamber 5 kgs. of nitrogen peroxide per hour were rendered innocuous at a consumption of heat amounting to about 3000 kg./cal. per kg. of nitrogen peroxide.

Having thus described the invention, what I claim is: r

1. A process for the disposal of gases containing nitrogen oxides originating from nitration reactions and the like, the oxides to be disposed of within a very short time in considerable amount in order to produce a gas mixture which is substantially free from nitrogenoxides and can be discharged safely without detrimental efiect on the environment, said process comprising forming a flame by the combustion of a carbon containing fuel with air, feeding the gases containing nitrogen oxides into said flame, the amount of fuel and air being sufficient to produce more than 2000 kilogram calories per kilogram of nitrogen oxide, calculated as N02, and the relative proportion of air and fuel being so chosen that no excess of atmospheric oxygen over the amount of fuel tobe burnt is present, and removing the gas mixture produced bythe said flame from the zone of the flame and discharging it to the atmosphere substantially free from nitrogen oxides.

2. A process forthe disposal of gases containing nitrogen oxides originating from nitration reactions and the'like, the oxides to be disposed of within a very short time in considerable amount in order to produce a gas mixture which is substantially free from nitrogen oxides and can be discharged safely without detrimental effect on the environment, said process comprising forming a flame by the combustion of a carboncontaining fuel with air, leading the gases containing nitrogen oxides into the reducing part of said flame, the amount of fuel and air being suilicient to produce more than 2000 kilogram calories per kilogram of nitrogen oxide, calculated as N02, and the relative proportion of air and fuel .being so chosen that no excess of atmospheric oxygen over the amount offuel to be burnt is present, .and removing the gas mixture produced by the said flame from the zone of the flame anddischarging it to the atmosphere substantially free from nitrogen oxides.

3..A processfor the disposal of gases containing nitrogen oxidesoriginating from nitration reactions and the like, the oxides to be disposed of within a very short time in considerable amount in order to produce a gas mixture which is substantially free from nitrogen oxides and can be discharged safely without detrimental eifect on the environment, said process comprising forming a flame by a combustion of a gaseous carbon containing fuel, feeding the gases containing nitrogen oxides into said flame, the amount of fuel and air being sufficient to produce more than 2000 kilogram calories per kilogram of nitrogen oxide, calculated as N02, and

therelative proportion of air and fuel being so can be discharged safely without detrimental effect on the environment, said process comprisingforming a flame by the combustion of an oily carbon containing fuel, feeding the gases containing nitrogen oxides into said flame, the amount of fuel and air being suflicient to produce more than 2000 kilogram calories per kilogram of nitrogen oxide, calculated as Nor-and the relative proportion of air and fuel being so chosen that no excess of atmospheric oxygen over the amount of fuel to be'burnt is present, and removing the gas mixture produced by the said flame from the zone of the flame and'discharging it to the atmosphere substantially free from nitrogen oxides.

PIERRE BARMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,487,647 Fauser Mar. 18, 1924 2,381,696 Shapleigh Aug. 7, 1945 OTHER REFERENCES Mellor: Comp. Treat. on Inorganic and 

1. A PROCESS FOR THE DISPOSAL OF GASES CONTAINING NITROGEN OXIDES ORIGINATING FROM NITRATION REACTIONS AND THE LIKE, THE OXIDES TO BE DISPOSED OF WITHIN A VERY SHORT TIME IN CONSIDERABLE AMOUNT IN ORDER TO PRODUCE A GAS MIXTURE WHICH IS SUBSTANTIALLY FREE FROM NITROGEN OXIDES AND CAN BE DISCHARGED SAFELY WITHOUT DETRIMETAL EFFECT ON THE ENVIRONMENT, SAID PROCES COMPRISING FORMING A FLAME BY THE COMBUSTION OF A CARBON CONTAINING FUEL WITH AIR, FEEDING THE GASES CONTAINING NITROGEN OXIDES INTO SAID FLAME, THE AMOUNT OF FUEL AND AIR BEING SUFFICIENT TO PRODUCE MORE THAN 2000 KILOGRAM CALORIES PER KILOGRAM OF NITROGEN OXIDE, CALCULATED AS NO2, AND THE RELATIVE PROPORTION OF AIR AND FUEL BEING SO CHOSEN THAT NO EXCESS OF ATMOSPHERIC OXYGEN OVER THE AMOUNT OF FUEL TO BE BURNT IS PRESENT, AND REMOVING THE GAS MIXTURE PRODUCED BY THE SAID FLAME FROM THE ZONE OF THE FLAME AND DISCHARGING IT TO THE ATMOSPHERE SUBSTANTIALLY FREE FROM NITROGEN OXIDES. 